The purpose of this phase III, multicenter study is to evaluate the safety and efficacy of intravenous bolus infusion of Lipo-PGE1 in two dose levels of 20 and 80 micrograms (mcg) in patients with atherosclerotic peripheral arterial occlusive disease and ischemic ulcers. The major endpoints for efficacy will be rate of ulcer healing, relief of pain and incidence of limb amputation.